Enzyme Structure and Cofactors:

• conjugated, catalytically active enzyme is called a holoenzyme, which consists of a protein component (apoenzyme) and a non-protein chemical component (cofactor).
• Statement (I) is CORRECT: Non-proteinaceous molecules required for an enzyme's biological catalytic activity are designated as cofactors.
• Statement (II) is CORRECT: Cofactors are broadly divided into two major groups:

• Inorganic ions / metal ions: Such as $\text{Fe}^{2+}, \text{Mg}^{2+}, \text{Mn}^{2+}, \text{Zn}^{2+}$ (essential for DNA polymerase, alcohol dehydrogenase, etc.).
• Organic molecules: Subdivided into coenzymes (transiently bound, e.g., NAD, FAD, CoA) and prosthetic groups (tightly/covalently bound, e.g., heme, biotin).

Statement (I) is true: The bacterial cytoplasmic (plasma) membrane follows the fluid mosaic model, composed of an amphipathic phospholipid bilayer with hydrophobic fatty acid tails oriented inward and polar hydrophilic phosphate heads outward.
Statement (II) is true: Because prokaryotes lack membrane-bound mitochondria, the bacterial plasma membrane hosts the electron transport chain, cytochromes, and ATP synthase complexes required for oxidative phosphorylation and energy (ATP) generation.

Matching crop diseases with their specific host crops:

• Tikka disease $\rightarrow$ Groundnut (IV): Caused by Cercospora arachidicola (early leaf spot) and Cercosporidium personatum (late leaf spot).
• Stripe (yellow) rust $\rightarrow$ Wheat (III): Caused by Puccinia striiformis f. sp. tritici, forming linear yellow stripes of uredinia on wheat foliage in cooler northern plains.
• Neck blast $\rightarrow$ Rice (I): Caused by Magnaporthe oryzae, attacking the panicle base/neck in paddy crops leading to rotten neck and empty chaffy grains.
• Fusarium wilt $\rightarrow$ Pigeonpea (II): Caused by Fusarium udum, causing vascular browning and catastrophic wilting in redgram.

Biology of Puccinia graminis f. sp. tritici:

• Urediniospores germinate to form appressoria over stomata and penetrate exclusively through open stomatal pores into the leaf/stem tissue: (A) is correct.
• As an obligate biotrophic rust fungus, it invades mesophyll cells by developing specialized intracellular feeding organs called haustoria: (B) is correct.
• As a macrocyclic heteroecious rust, its alternate sexual hosts are woody dicot shrubs (Barberry, Berberis vulgaris and Mahonia spp.), where pycnia and aecia are produced: (D) is correct.
• Puccinia graminis f. sp. tritici is highly forma specialis-specific to wheat and does not maintain collateral weed hosts in plain wheat fields (unlike stripe rust): (C) is not typical.